[LEDE-DEV] [PATCH] BT Home Hub 5A: configure Red Ethernet as DMZ interface (FS#490) and fix Red Ethernet switch port (FS#390)

Mauro Mozzarelli mauro at ezplanet.net
Fri Feb 17 02:42:26 PST 2017

The BT Home Hub routers described in the scenario(s) below are connected 
also on the LAN side.

I ran further tests in the first SCENARIO (Red Ethernet as eth0.2) 
monitoring the red Ethernet WAN end with wireshark and I saw arp 
requests coming from the Red Ethernet that have both mac address and IP 
that belong to the LAN port. I saw also arp requests with the correct 
mac and IP from the Red Ethernet, but these requests did not get a reply 
when the destination was another BT Home Hub 5 with the same 
configuration (and only in that case). Both routers were on the same 
subnets on LAN on the Yellow switch and WAN on the Red Ethernet.

This does not happen with the unmodified code where the Red Ethernet is 
configured as eth1.2.

It looks like the Ethernet ports get into an identity crisis with the patch.


On 16/02/17 17:37, Mauro Mozzarelli wrote:
> Mathias,
> I have just come across a weird side effect of the following change. 
> With the patch applied it is no longer possible to communicate via the 
> red Ethernet between 2 BT Home Hub 5, but communications are fine 
> between a HH5 and any other device (??).
> diff --git a/target/linux/lantiq/dts/BTHOMEHUBV5A.dts 
> b/target/linux/lantiq/dts/BTHOMEHUBV5A.dts
> index 7f19e52..59b6cee 100644
> --- a/target/linux/lantiq/dts/BTHOMEHUBV5A.dts
> +++ b/target/linux/lantiq/dts/BTHOMEHUBV5A.dts
> @@ -244,15 +244,6 @@
>             phy-mode = "gmii";
>             phy-handle = <&phy13>;
>         };
> -   };
> -
> -   wan: interface at 1 {
> -       compatible = "lantiq,xrx200-pdi";
> -       #address-cells = <1>;
> -       #size-cells = <0>;
> -       reg = <1>;
> -       lantiq,wan;
> -
>         ethernet at 5 {
>             compatible = "lantiq,xrx200-pdi-port";
>             reg = <5>;
> ------------------------------------------------------------------------------- 
> With the above patch applied (and changing board.json to include port 
> 5) the red Ethernet appears as eth0.2
> SCENARIO with above patch applied:
> red Ethernet appears as eth0.2 and assigned an IP
> 2 x bt (BTHomeHub5) routers (a and b) plus other devices (od)
> bt(a), bt(b) and od have eth0.2 on the same subnet
> ping bt(a) --> bt(b) no response (tcpdump shows arp request from bt(a) 
> mac address and no arp response from bt(b)
> ping bt(b) --> bt(a) as above
> ping bt(a or b) --> od  OK
> ping od --> bt(a or b) OK
> SCENARIO without above patch applied
> red Ethernet as eth1.2 and bridged (it does not work if I do not 
> create a bridge and assign eth1.2 to the bridge, but we knew this)
> ping bt(a) --> bt(b) OK
> ping bt(b) --> bt(a) OK
> ping bt(a or b) --> od  OK
> ping od --> bt(a or b) OK
> Mauro
> On 13/02/17 07:27, Mathias Kresin wrote:
>> 12.02.2017 17:40, Mauro Mozzarelli:
>>> You are correct that the name does not matter, however if we have
>>> routers already configured to associate the xDSL or Ethernet to WAN,
>>> when we flash the new firmware we will have to reconfigure them to
>>> rename the device. This is all good if the routers are physically 
>>> there,
>>> but when the routers are in remote unmanaged locations (like I have) it
>>> becomes a problem. Renaming the interface is a small thing, but it will
>>> impact many end users. I advocate to maintain WAN for xDSL out of my 
>>> use
>>> case interest and also because personally I think an xDSL is truly a 
>>> WAN
>>> interface whilst an Ethernet can be anything.
>> Please keep in mind that your existing config is not touched and the 
>> wan network still exists with my patches applied. I fail to see how 
>> it should break existing xDSL configs.
>> But you are right, the ethernet wan config will most likely not work 
>> any longer for people who managed to workaround all the outlined 
>> issues. But the same applies to your patch, since you are moving the 
>> ethernet wan from eth1 to eth0 as well. Lets hope that only the 
>> minority of the uses managed to configure a working ethernet wan.
>> Mathias
>> _______________________________________________
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>> Lede-dev at lists.infradead.org
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Mauro Mozzarelli
eMail: mauro at ezplanet.net
Phone: +44 7941 727378

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